A Muslim may ask:
According to this grace idea, anyone can sin since God forgave us. Why not I just go and sin then?
You might think that you have a license to sin since forgiveness and restoration to eternal life in paradise is a free gift of God’s grace.
Well, that is not right. You can not just sin because there is a free gift of grace. One of Jesus apostles (Paul) addressed the same issue raised by the misunderstanding of the free gift of salvation. (Romans 6)
The same question was raised at his time, he addressed it saying:
“What shall we say then? Are we to continue in sin that grace may abound?” (Romans 6:1)
Paul’s answer the question he posed:
“By no means! How can we who died to sin still live in it? Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death? We were buried therefore with him by baptism into death, in order that, just as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life.” (Romans 6:2-4)
The death of Christ was death because of the sin of human beings, he died for their sins. When we confess faith in Christ’s work, we also die like him to sin and resurrect to life.
“For the death he [Christ] died he died to sin, once for all, but the life he lives he lives to God. So you also must consider yourselves dead to sin and alive to God in Christ Jesus.” (Romans 6:10-11)
Apostle Paul conclude that we have to avoid sin.
“Let not sin therefore reign in your mortal body, to make you obey its passions” (Romans 6:12)
As you see free gift of salvation does not include a license or permission for sin.